Not applicable.
Not applicable.
The present invention relates to corona treatment apparatus in general, and to adjustable electrode arrangements for corona treatment apparatus in particular.
Often a substrate will be selected for use in some practical application based on desirable material properties or economic efficiencies. At times, however, where it is necessary to imprint or coat the selected substrate, difficulties may arise in causing the ink, paint, dye, adhesive or other coating to adhere to the substrate. This is often the case, for example when printing on plastic films.
While the plastic film may have desirable qualities of durability, flexibility, and capability for forming an airtight package, many plastic substrates are unsuitable for conventional printing techniques in an untreated condition.
The corona treating apparatus positions an electrically conductive emitting electrode in close proximity to a substrate web as it travels over a conductive electrode roller. An AC current is discharged from the emitting electrode, and passes through the substrate to the electrode roller. In the process, portions of the substrate surface are ionized and thereby caused to bond with atmospheric oxygen molecules. When a substrate such as a plastic film passes through the corona, ions cross-link a positive free radical to the surface of the substrate. The regions of the surface so treated are made, for a time, receptive to bonding with the coating which is applied shortly after the corona treatment.
Corona treatment is used in the preparation of packaging, labels, plastic articles, and other common products. Because it is only necessary to treat those regions of the substrate which will receive printing or coating, it is desirable to curtail corona discharge in those regions where treatment is not required. Moreover, heat sealing of plastic is difficult or impractical once a region has been corona treated. Corona discharge activity can be avoided by increasing the distance between the emitting electrode and the electrode roller, often by only fractions of an inch.
Segmented electrodes have been employed in corona treatment apparatus which have segments which are held in a non-active condition by a friction fit by being clamped between two channels. However, there is the possibility that segments held in a friction fit can come loose as a result of vibrations over time.
What is needed is a corona treating apparatus in which the electrode spacing from the substrate may be conveniently and expeditiously adjusted along the length of the electrode.
The corona treating apparatus of this invention has an electrically conductive electrode housing with a downwardly opening channel, within which are adjustably positioned a number of conductive electrode segments. The segments have a stem which extends into the channel, and a foot which extends below the channel and which overlies an electrically conductive electrode roller, over which the material to be treated travels. Top springs extend into bores in the top of the electrode segments, and ball detents extend through the housing to urge against slots on one side of the segments. Each electrode segment stem has two upper lips, a first lip which engages with an upper ledge when the segment is in a retracted position, and a second lip which engages with a lower ledge on the opposite wall when the segment is in an active position. By pushing upwardly on one sideward flange of an electrode foot, the user readily changes the position of each segment.
It is an object of the present invention to provide an electrode for a corona treatment apparatus which is readily configured to treat different sized substrates.
It is another object of the present invention to provide an electrode for a corona treatment apparatus which is adjustable by hand to treat or not treat axial lengths of a substrate running therebeneath.
It is also an object of the present invention to provide a segmented electrode for a corona treatment apparatus in which the electrode segments are independently adjustable.